A Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometer (MALDI-TOF MS) is an example of a spectrometer, which is used to detect attributes of a sample. For example, the sample may be human blood and the detected attributes may be diseases or other medical conditions of the person from whom the blood was drawn. There are other applications for spectrometers aside from disease diagnosis.
However, there are challenges in using MALDI-TOF MS for disease diagnostics in a clinical environment. One challenge is that there may be poor reproducibility of mass analysis data. The reproducibility in intensity for each mass-to-charge may be a critical factor for diagnostic accuracy when the diagnostics requires the information about intensity in addition to mass-to-charge information, such as in the case of cancer diagnostics or status check of diseases.
Another cause of the poor reproducibility may be from the MALDI-TOF's intrinsic character in ion optics. A MALDI-TOF MS may be able to analyze samples relatively quickly with high sensitivity. In some circumstances a MALDI-TOF MS may be a relatively poor quantitative analysis tool because all the ionized particles do not have the same initial velocities at the chamber entrance and/or do not travel the same distance in the chamber due to the different incident angles of particles. Accordingly, there may be an inevitable data spread over time lowering data reproducibility.
In some circumstances, after MALDI-TOF MS ionization of a sample, the data is calibrated and adjusted into a mass-to-charge ration (m/z), which may be represented as mass peaks with a statistical variation. When a spectrometer measures the time-of-flight of an ionized particle, the measured time-of-flight can be converted to a mass-to-charge ratio using a quadratic equation. Unfortunately, there is some variation in the time-of-flight of ionized particles due to imperfections of spectrometers. Accordingly, the same types of ionized particles may have a statistically distributed time-of-flight measurement. For spectrometer data to be optimized for matching profiles from a reference library, the statistical variation of time-of-flight measurements should have a minimized standard deviation. When time-of-flight measurements are converted to mass-to-charge ratios using a quadratic equation, the standard deviation of the time-of-flight measurement is compromised, which may make it difficult to associate attributes to a sample (e.g. difficult for a human blood sample to produce a diagnosis in a MALDI-TOF MS).